Elastomers from polyalkylene ether glycol reacted with arylene diisocyanate and water



Patented Oct. 26, 1954 UNIT-ED STATES PATENT QFFICE 2,692,873 ELAs roMEits FROMPdLYALKYLENE ETHER GLYCOL REACTED WITH ARYLENE DIISO- AND WATER Esley Langerak, Newport, and Lawrence J.

P i i a d W ll It Remington, Wilmington, Del, assi'gnors'to E. I. du Pont de Nemours & "C'dihpan'y, Wilmington, DeL, a corporation nrDenw-are No Drawing. Application May 1'7, 1952,

Serial Noil f288gfi3l 1 13 Claims. This invention relates to an; improved process for the preparation of claston'leric condensation products from the reaction between polyalk-yle'ne ether glycols and a'rylne au'sscyamt'es.

it is well known that dii'socyahates ma hereacted with dihydroxy can ound's to form "c'o'ndensation products or capbiyniers. Many of these products are thermoplastic resins. In Hill U. S. application Serial Iio. 237, 660, filed July 19, 1051, now abandoned, there is described the formation of tough rubbery products by the reaction between polyalkylene ether glycols and arylene diisocyanates in the presence oi moisture. Useful elastorners are obtained by this process, for example, by the reaction of a polyethylene ether glycol having a molecular weight of from 4000 to 10,000 with tolylene-2A-diisocyanate in the presence of small amounts of water.

According to the present invention, it has been found that an improved product is obtained when the reaction: between the polyalkylene ether glycol, arylene diisocyanate and wateris carried, out in the presence of; small amounts of an acid-reacting compoundselected irorr the group consisting of acid halides in whichthe halogen has an atomic weight between 35 and l27andinorganic acids. l H

In a preferred embodiment of this invention, the polyalkylene ether glycol and the arylene cliisocyanate are heated togetherlin the presence of the acid-reacting cornjpound but Without any added water, in order to form a pre -polymer, and water is thereafter incorporated inthe mixture and the composition is cured to form the ultimate elastomer.

The method of carrying out the process of this invention is illustrated by the following examples, in which parts are by weight:

Eaiztmple 1 Into a glass vessel are placed 58 parts of a polymeric ethylene ether glycolof average molecular weight 1540. This is melted by warming externally with steam to 80" C. There are then added 27.8 parts of toly1ene-2A-diisocyanate and. 0.12 part of benzoylchloride .(rnolarratio of iso cyanate to glycol 4:l). The mixture is heated for 2 hours at '80? C. The viscous amber-colored solution is transferred to a Werner-Pfleide'rer millwhich has been preheated to 759. C. The mass is then milled and 0A7 part of pyridine is added, followed. immediately by 2.0 parts of water. The mass is milled for 1 hour at 75 Then 2.0 additional parts of water are added. In 20 minutes the product shreds off the millblades in rubbery chunks and is then removed from the mill.

The rubbery chunks are cured by putting a 51; quantity in a press having a rectangular die and heating for 1 hour at 140 C. under a pressure of 2,800 lbs. per sq. in. A transparentslab results which has the following properties:

Tensile strengthu u u lbs/sq. in 2225 erceritelong'ation atthe'break'mer' cent 280 Brittle point; 0-- -42.a Modulus at 200% eldngation lbs./sq. in. 1550 In a control experiment carried out in the same way except that no benzoyl chloride is "added, the primary condensation product is a solid, porous, spongy mass. On milling in the W-P mill the product yields a mass of soft crumbs. On curing for 1 hour at 140 C. under 0,000 lbs. per sq. in. pressure a coherent mass is not obtained. On continuing the cure for 18 hours, ablar, yellow, non-homogeneous slab is obtained which is so weak that it can be torn by hand.

Example 2 Using the same equipment as in Example 1, 60. parts of 'a polyethylene ether glycol of average molecular weight 1000 are warmed to C. and 31.3 parts of tolylene-2,4-diisocyanate containing 0.06. part of phosphorus pentachloride are added (incl ratio "of isacyanate to glycol 3:1); The mixture is stirred "and held for 1 hour at 100 0. Then 0.47 part of pyridine is added and after thorough mixing the viscous solution is transferred to the W-P mill which has been preheated to 75 C. The nillis started, 4.0 parts of Water are added and milling is continued for 40 minutes, when the product shreds off in tough rubbery chunks;

on curing for 1 hour at C. at 2,800 lbs. per sq'. in. pressure a. cle"ar, transparent, homogeneous, amber colord slab isobtained. The elastomer possesses the following properties:

The process o f '2 is repeated using 0.138 part of. benzene sulfonyl chloride in place of the phosphoriis pentachloride. After curing, the product has the following properties:

Tensile strength lbs./sq. in 3275 Elongation at break per cent 540 Brittle point C -40 Modulus at 200% el0ngation' lbs./sq. in 1000 Efiutthle '4 "'rhepfbtess o'f transits repeated using 0106 part of hydrogen chloride, added as 0.162 part of a 37% aqueous solution, in place of the phosphorus pentachloride. Six (6) parts of water are added instead of 4. The balance of the process is then the same. The cured product has the same appearance as that of Example 2 and has the following properties:

Tensile strength lbs./sq. in 1000 Elongation at the break per cent 480 Brittle point f C -45.6

Modulus at 200% elongation lbs./sq. in 600 Example 5 The process of Example 2 is repeated using 0.12 part of p-methoxy benzoyl chloride in place of the phosphorus pentachloride. The properties of the resulting rubber are as follows:

Tensile strength lbs./sq. in 650 Elongation at break per cent 580 Brittle point C -37 Modulus at 200% elongation lbs./sq. in 4'75 Example 6 The process of Example 2 is repeated using 0.11 part of 100% sulfuric acid, added as sulfuric acid, in place of the phosphorus pentachloride. The rubber obtained has the following properties:

Tensile strength lbs./sq. in .1270

Elongation at break per cent 480 Brittle point C -45 Modulus at 200% elongation lbs./sq. in 500 Example 7 The process of Example 2 is repeated using 0.164 part of thionyl chloride in place of the phosphorus pentachloride. Rubber having the following properties is obtained:

lensile strength llos./sq in 3150 Elongation at break per ccnt 500 Example 8 The process of Example 2 is repeated using 0.25 part of p-toluene sulfonyl chloride in place of the phosphorus pentachloride. The rubber obtained has the following properties:

Tensile strength lbs./sq in 850 Elongation at break per cent 400 Example .9

One hundred (100) ether glycol of an average molecular weight of 1025 are stirred in a glass vessel at 100 C. for 1 hour with 52.2 parts of tolylene2,4-diisocyanate and 0.19 part of phosphorus trichloride. The resulting thick liquid is transferred to a Werner- Pfieiderer mill previously heated to 75 C. The.

mill is started and :there is added 0.637 part of pyridine and 4.0 parts of water. After milling at 75 C. for 30 minutes, an additional 2.6 parts of,

parts of a polypropylene- Tensile strength lbs./sq. in 4150 Elongation at break per cent 380 Modulus at 300% elongation lbs./sq, in 2225 Brittle point C 42 Example. 10;

Into a Werner-Pfleiderer mixer preheated to C. are placed 99 parts of n-butylene ether glycol of an average molecular weight of 10,000. After the glycol is melted, 26.1 parts of tolylene- 2,4-diisocyanate and 0.38 part of phosphorus trichloride are added. This amount of phosphorus trichloride is required because a 5% aqueous slurry of the glycol shows a pH of .3. After the addition, the reaction mass shows a pH of 4 on general purpose indicator paper. The mass is then milled 1 hour at 100 C. A clear yellow viscous liquid results. A total of 1.2 parts of pyridine and 3.0 parts of water is then added with continued milling in three equal increments at intervals of 20 minutes. The temperature is held at 100 C. during this time. At the end of 30 minutes after the last addition the product is in the form of white doughy chunks. The mass is then worked on a rubber mill at 30C. to a smooth homogeneous white band.

A portion is cured in a mold at 140 C. under 2800 lbs. per sq. in. pressure for 1 hour. An opaque, cream-colored slab is obtained It is tough and rubbery and has a tensile strength at the break of 4800 lbs. per sq. in.

Example 11 Thirty-three (33) parts of a polyalkylene ether glycol of the general formula HO(C2I-I4OCHZO)1H with an average molecular weight of 16 0 are thoroughly mixed with 13.9 parts of tolylene-2,4- diisocyanate and 0.05 part of benzene sulfonyl chloride and heated at IOU- C. for 1 hour in a closed container. The mixture is then cooled to 90 C. and 0.3 part of pyridine and 1.4 parts of water are added and thoroughly mixed in. The resultant viscous mass is poured into a pan and baked in an oven at 80 C. for 30 minutes. The somewhat tacky solid mass is then milled on a cold rubber mill to form a smooth homogeneous band. A portion is cured by heating in a mold at C. for 30 minutes under a pressure of 70 0 lbs. per square inch. A soft, elastic and transparent slab is obtained.

The term polyalkylene ether glycols as used throughout the specification and claims refers to polyethers which are derived from alkylene oxides or glycols or from other heterocyclic others such as dioxolane, and which may be represented by the formula HO (R0) nH in which R stands for an alkylene radical such as methylene, ethylene, propylene, etc. and n is an integer greater than 1. Not all of the alkylene radicals present need be the same. Glycols containing a mixture of radicals, as in the compound HO(CH2OC2H4O)1LI-I, can be used. liquids or waxy solids. The glycols which are useful in the process of this invention have molecular weights of at least 750 and may have molecular weights as high as 10,000. The preferred glycols are the polyethylene ether glycols, the polypropylene ether glycols and the polybutylene ether glycols.

Any of a wide variety of arylene diisocyanates may be employed in this process. Representative compounds include tolylene 2,4 diisocyanate, meta-phenylene diisocyanate, l-chlorophenylene- 2,4-diisocyanate, and naphthalene-1, -diisocyanate. These compounds may contain other substitutents on the aryl rings and the isocyanate groups may be attached'to the same or different 2:1 and 12:1, although mixtures in other proportions may be used. When using a polyalkyl- These glycols are either viscous ene ether glycol of relatively low molecular weight, e. g., from 750 to about 3000 ,.the molar ratio of diisocyanate to. glycol is. preferably. between 2: l and 7:1- With higher molecular. weight glycols, a higher ratio of diisocyanate to glycol is desirable. Thus .for a glycol of molecular weight 6000 the preferred ratiov is .from 8:1. to 12:1, while for a glycol of molecular weight 1000, the preferred molar ratio is about 3.: l.

The acid-reacting compound which is added according to this invention is an acidchloride, an acid bromide, an acid iodide or: an inorganic acid. When anacid halide is used, it. may be derived from. either an organic acid or an inorganic acid. Representative and useful members of thisv class of compounds are hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, phosphoric acid, acetyl. chloride, acetyl bromide, benzenesulfonyl chloride, sul-furous oxybromide, sulfurous oxychlorid'e, phosphorus tri bro'nide, phosphorus trichloride, phosphorus pentachloride, phosphorus oxychloride, phosphorus oxybromide, and benzoyl' chloride. Simple organic halides such as benzyl chloride are not operable. Acid fluorides are in general too volatile to be useful in this process. Free carboxylic acids such as acetic, benzoic, etc. cannot be used as they react with the isocyanatewith liberation of carbon dioxide.

Some benefit is obtained from the use of less than about 0.1% of the acid-reacting. substance, based on the weight of the isocyanate, but the results are less satisfactory than if higher amounts are employed. When more than 0.5% of the acid-reacting substance is used, the physical properties such as. tensile strength and abrasion resistance of the resulting elastomers tend to be somewhat impaired. If any component of the reaction mixture contains appreciable amounts of alkaline materials, it is of course necessary to employ increased amounts of acidreacting substances to neutralize this alkalinity. As the glycol is more apt to be alkaline than the diisocyanate, it is well to add the acid-reacting substance in such amount that a dispersion or solution in water of a mixture of it with the glycol shows a pH of 6.0 or less.

The acid-reacting substance may be added at the time of mixing the glycol and diisocyanate,

may be incorporated with either or both of the reactants prior to mixing, or may be added after mixing has taken place but prior to the addition of water. The resulting composition must be on the acid side, though the actual acidity cannot be measured accurately by the pH of a water solution, since the diisocyanate reacts with the water to yield 002. An approximation of the true pH may be obtained by the use of general purpose indicator papers.

It is necessary that at least the latter stages of the reaction be conducted in the presence of water, preferably in amounts from 0.5 to 1.5 moles per mole of arylene diisocyanate. This amount of water is added to the mixture unless the components of the reaction mixture already contain a sufiicient amount of water. If greater amounts of water are present, the excess acts as a plasticizer for the rubbery product. With smaller amounts, the reaction proceeds more slowly and does not always go to completion or results in a product not having the desired physical properties.

Although the mechanism of the reaction is not fully understood, it is believed that it involves first a copolymerization of the glycol and ing point of the glycol.

The only .anate in the presence of between 750 and 10,000

the diisocyanate to form. linearachains contaim ing urethane linkages. Excess diisocyanatemay then react with water to give substituted ureas which are capable of further reaction. with the original linear polymers, Inthisway the linear polymers, which may be referred torasitheprepolymers, are cross-linked and extended toiform the ultimate elastomeric product. The. function of the acid-reacting substance iii-this process appears to be to prevent premature; cross liuhing of the linear polymers and resim'fication of the reaction mixture.

It is desirable to. conduct thereactionin two steps. During. the first step the preepolymer is formed in the substantial. absence. of. water, and during the second. step. water isadded and cross-linking takes. placeto form the final product. In this way, greatercapacity can. be ob.- tained with the samemixing equipment. since during the pres-polymerization step, the mixture is liquid and easily agitated. whereas inthe final condensation step, more strenuous agitation is required. The Werner-Pileiderer: mill: is typical of suitable mixing equipment of the: latter sort. The mixing equipment may be of any desired construction but should be resistant to acid and to the other reactants.

As the reaction is carried out in the liquid phase, the temperature should be above; the melt- Generally, temperatures of 50 to C. are. satisfactory. From one to two hours reactiomtime: is: ordinarily adequate to complete the pro-polymerization step, and a somewhat shorter; time forsthe condensation step.

detrimental eifect ofiusing longer reaction times which has been observed is a gradual darkening of the coloring ofzthc product...

Elastomers prepared according to the process of this invention have better tensile strength and modulus of elasticity and are more risistant to abrasion than are the similar products prepared according to the prior art. The present process employing an acid-reacting substance during the condensation is of particular value with the lower molecular weight glycols, especially with polyethylene ether glycol of relatively low molecular weight. With such glycols, unless the acid-reacting substance is used, there is a tendency to form gels which are not easily converted to elastomeric products. With the acid-reacting substance present, however, elastomers of excellent strength and elasticity may be obtained. By the use of the present process the reaction proceeds smoothly and more reproducibly than in the absence of the acid-reacting substance.

What is claimed is:

1. In a process for preparing an elastomeric condensation product by heating together a polyalkylene ether glycol having a molecular weight with an arylene diisocywater, the improvement which comprises carrying out the heating in the presence of from 0.1 to 0.5%, based on the weight of diisocyanate, of an acid-reacting compound selected from the group consisting of acid halides in which the halogen has an atomic weight between 35 and 127 and inorganic acids.

2. A process according to claim 1 in which the polyalkylene ether glycol is a polyethylene ether glycol.

3. A process according to claim 1 in which the polyalkylene ether glycol is a polypropylene ether glycol.

4. A process according to claim 1 in which the 7 polyalkylene ether glycol is a polybutylene ether glycol.

5. A process according to claim 1 in which the arylene diisocyanate is toly1ene2,4diisocyanate.

6. A process according to claim 1 in which the arylene diisocyanate is meta-phenylene diisocyanate.

'7. In a process for preparing an elastomeric condensation product by heating together a polybutylene ether glycol having a molecular weight between 750 and 10,000 with tolylene-ZA-diisocyanate in the presence of water, the improvement which comprises carrying out the heating in the presence of from 0.1 to 0.5%, based on the weight of diisocyanate, of an acid-reacting compound selected from the group consisting of acid halides in which the halogen has an atomic weight between 35 and 127 and inorganic acids.

8. A process for preparing an elastomeric condensation product which comprises heating together at a temperature between 50 and 100 C. a polyalkylene ether glycol having a molecular weight between 750 and 10,000 and an arylene diisocyanate in the presence of from 0.1 to 0.5%, based on the weight of diisocyanate, of an acidreacting compound selected from the group consisting of acid halides in which the halogen has an atomic weight between 35 and 127 and inorganic acids, the molar ratio of diisocyanate to glycol being between 2:1 and 12:1, incorporating in the mixture 0.5 to 1.5 moles of water per mole of diisocyanate and thereafter curing the composition.

9. A process according to claim 8 in which the polyalkylene ether glycol is a polyethylene ether glycol.

10. A process according to claim 3 in which 8 the polyalkylene ether glycol is a polybutylene ether glycol.

11. A process according to claim 8 in which the arylene diisocyanate is tolylene-ZA-diisocyanate.

12.'A process for preparing an elastomeric condensation product which comprises heating together at a temperature between 50 and C. a polybutylene ether glycol having a molecular weight between 750 and 10,000 and a tolylene- 2,4-diisocyanate in the presence of from 0.1 to 0.5%, based on the weight of diisocyanate, of an acid-reacting compound selected from the group consisting of acid halides in which the halogen has an atomic weight between 35 and 127 and inorganic acids, the molar ratio of diisocyanate to glycol being between 2:1 and 12:1, incorporating in the mixture 0.5 to 1.5 moles of water per mole of diisocyanate and thereafter curing the composition.

13. In a process for preparing an elastomeric condensation product by the reaction of a polyalkylene ether glycol having a molecular weight between 750 and 10,000 with an arylene diisocyanate in the presence of water, the improvement which comprises adding prior to any substantial reaction between the water and the other components from 0.1 to 0.5%, based on the weight of diisocyanate, of an acid-reacting compound selected from the group consisting of acid halides in which the halogen has an atomic weight between 35 and 127 and inorganic acids.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,531,392 Breslow Nov. 28, 1950 

1. IN A PROCESS FOR PREPARING AN ELASTOMERIC CONDENSATION PRODUCT BY HEATING TOGETHER A POLYALKYLENE ETHER GLYCOL HAVING A MOLECULAR WEIGHT BETWEEN 750 AND 10,000 WITH AN ARYLENE DIISOCYANATE IN THE PRESENCE OF WATER, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE HEATING IN THE PRESENCE OF FROM 0.1 TO 0.5%, BASED ON THE WEIGHT OF DIISOCYANATE, OF AN ACID-REACTING COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACID HALIDES IN WHICH THE HALOGEN HAS AN ATOMIC WEIGHT BETWEEN 35 AND 127 AND INORGANIC ACIDS. 